The present invention relates to a wire stitching or stapling machine of the type which severs and forms staples from a continuous wire and drives the staples into an associated workpiece. In particular, the invention relates to a stitching head for such a machine. Such machines are useful in a variety of applications, such as in bindery, the stapling of cartons or other containers, as well as other types of stapling.
The present invention is an improvement of the wire stitching machine sold by Interlake, Inc., the assignee of the present invention under the trademark "CHAMPION STITCHER". This prior stitching machine, which is in turn an improvement of the machine described in U.S. Pat. No. 1,252,011, includes a stitching head having a wire feed mechanism for feeding a predetermined length of wire from a continuous wire supply to a wire holder, where the length of wire is severed from the supply, and a staple-forming and driving mechanism which forms the severed length of wire into a staple and drives it into an associated workpiece. The wire feed means and the staple-forming and driving means are coupled together so that they undergo a reciprocating movement in tandem, moving together in the same direction in response to an associated drive. Thus, the mechanism undergoes a cyclical reciprocating movement comprising a drive stroke and a return stroke. During each drive stroke the feed means is feeding a predetermined length of wire to the wire holder, while the staple-forming and driving means is forming and driving the length of wire which had been fed during the preceding drive stroke. Both mechanisms then retract simultaneously, and at the end of each cycle there is left in the wire holder a severed length of wire ready to be formed and driven during the next drive stroke.
This type of stitching head operates well in normal heavy duty operations which typically involve very long runs, comprising many thousands of cycles of stapling the same material or material of the same thickness. However, such heads have been found to be unsuitable for use in office applications for the stapling of documents and the like, wherein there are frequent changes in the thickness of the work to be stapled. In the typical office application, it is not uncommon for the thickness of the work being stapled to be changed every few cycles of the machine. This has proven to be an inconvenience with the aforementioned prior heads since, each time the head is adjusted to change the wire draw and the length of staple to be formed and driven, the severed length of wire left in the wire holder from the previous cycle must first be removed. Not only does this necessitate an additional step in the adjustment or change-over operation, but it also creates a waste removal problem. The discarded lengths of wire frequently wind up littering the floor and this has proved to be a considerable disadvantage in the use of the machine.